1. Field of the Invention
The present invention is directed to waterproof breathable insulation material and in particular such material for use in outdoor clothing and boots.
2. Description of the Related Art
Outdoor enthusiasts have continually demanded technically advanced gear to protect themselves from the elements. This demand resulted in the development of several waterproof, breathable fabric constructions where the fabric is typically laminated to thin films or membranes. Waterproof breathable fabrics have been used in performance garments for many decades and have proven to be a preferred performance component. Both the prevention of water reaching the body from outside the clothing, and the removal of vapor produced by the body are of great importance to the wearer in terms of comfort. However, the disadvantage to such fabrics has always been that although they are classified as being breathable, they do not offer significant moisture vapor transport. Further, most breathable fabrics tend to have very limited insulating properties. Still further, fabrics laminated to certain types of membrane types tend not be very flexible and generate noise when in use. Accordingly, despite their claims most waterproof breathable fabrics tend to be less breathable than desired, offer limited insulating properties so that they must be used in conjunction with some form of insulating material, and require the user to endure their stiff and noisy nature.
Insulating materials are often used in conjunction with or incorporated into performance garments to provide for thermal protection. However, most insulating materials do not provide for water repellency or alternatively provide water repellency at the cost of a corresponding diminution in thermal protection. PrimaLoft® insulation, as described in U.S. Pat. Nos. 4,992,327 and 4,588,635 and incorporated herein by reference, is unique to the synthetic insulation world in that it offers superior water repellency in addition to the thermal performance indicative of the micro and fine fiber construction.
However, PrimaLoft® insulation has been primarily used as a replacement for natural down with the added benefit that it is waterproof. Alternatively, PrimaLoft® batt has incorporated into clothing manufacture where it is a separate insulating layer. Often it is mechanically secured to other layers of woven or non-woven material for example through quilting. However, the PrimaLoft® insulation by itself does not have sufficient structural integrity, or aesthetic appearance to suffice as both an insulating material and an outer garment layer.
Another element of many waterproof breathable fabrics are monolithic membrane films, which are used to impart a breathable barrier to the fabric. Monolithic membranes promote the permeation of water vapor through the use of a hydrophilic polymer layer which absorbs the water next to skin and transmits it to the external environment.
Unfortunately, monolithic films typically experience significant swelling of the hydrophilic layer which significantly alters the vapor removal characteristics of the film and the comfort for the user. Further, although this type of membrane also has a very high tear strength, which is generally favorable in performance fabrics, this also results in extraordinary stiffness in a garment that is usually not viewed as a positive attribute.
Accordingly, there is a need for an waterproof, breathable, insulation material which provides superior water repellency or waterproofing characteristics coupled with superior vapor removal characteristics which will not swell and has sufficient tear strength, but which is not unduly stiff or noisy for the wearer.